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Chapter 30
Fish
360 to 400 million years ago-
Jawless Fish
These are the most primitive vertebrates.
A hagfish.
A sea lamprey.
Lamprey on trout
IV. Fishes
A. Vertebrate jaws evolved from skeletal supports of
Jaws and fins allowed fish to become active in pursuit of
food and in biting off chunks of flesh.
Members of group are chondrichthyes and osteichthyes.
They have two pairs of fins.
Respiratory Structures
• Gills
• Made of feathery thread-like structures called
filaments. Each filament contains a network of
capillaries for the exchange of oxygen and carbon
dioxide.
• Fishes exchange gases by pulling oxygen-rich
water in through their mouths, pumping it over
their gill filaments, and then pushing oxygen-poor
water out through gill openings.
Circulation in fish
Two
chambered
heart
360 to 400 million years ago- the “Age of Fishes”
Two groups are alive today: Class
Chondricthyes: Sharks and Rays have cartilaginous
skeletons.
Skin made of
denticles
Nerve center
Stream lined
body
Liver secretes oil to change depth Rigid Pectoral fins used for lift
Shark Skin
• Shark skin feels like
sandpaper because it has
small scales known as
denticles. It is often dried
and used as a leather product
or sandpaper. Denticles are
homologous in structure to
teeth, and are what gives the
skin a rough feeling.
Ampullae
Counter shading
Osteichthyes: “bony fishes”
Paired fins that move independently
swim bladder to change depth quickly
lateral line: line of sensitive nerve endings
Scales for protection and flexibility
Ray finned
Lake trout
Whitefish
Ray
finned
Sturgeon
Great Lakes
Walleye
Some of the natives
Lobe finned fishes
Coelacanth
Sea to land
Excretion.. Lol c:
• Kidney
– Helps control the amount of water in their
bodies.
– Fish in saltwater tend to lose water, so
their kidneys concentrate the waste in the
form of ammonia, which contains very
little water and helps control water loss.
– Fish in freshwater tend to gain water, so
their kidneys produce very dilute urine
which contains an abundance of water.
Fish
Spawning: females laying eggs
and males fertilizing them
externally
•Roe: fertilized fish eggs
•Milt is the seminal fluid
from males that fertilizes
The eggs
Fry: baby fish
Reproduction
• Internal or external fertilization.
• Oviparous- Female lays the eggs and the
embryos in the eggs develop and hatch
outside her body.
• Ovoviviparous- The eggs stay in the
mother's body after internal fertilization and
embryo develops inside egg and obtain
nourishment from the egg; the young are
“born alive”.
• Viviparous- The embryos stay inside the
mother’s body after internal fertilization and
obtain nourishment from mother’s body, not
egg; the young are “born alive”.